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<div>The Pacific Western US is the main producer of red raspberry (<i>Rubus idaeus</i>) in the world. The most common plant pathogen causing disease in raspberry fields in the PNW is <i>Phytophthora rubi</i>, an oomycete plant pathogen known to cause red root disease in red raspberry. <i>P. rubi</i> is found in 90% of raspberry crops in the state of Washington, resulting in millions of dollars in losses to the berry industry of the United States. A recent study showed an absence of population structure in <i>P. rubi</i> across the PNW, indicating that constant migration might be taking place. To study the population dynamics of <i>P. rubi</i>, we used genotyping-by-sequencing (GBS) to characterize diversity and study population structure and migration between West coast states of the US. To determine interconnectivity and migration between states we evaluated several demographic scenarios using DIYABC. Our results show that <i>P. rubi</i> forms a single population in the PNW, and has high rates of migration between geographic locations. Analysis of directed migration show that nurseries in the state of Washington are sinks of disease from nurseries in California and Oregon, most likely due to the transport of contaminated soil and plant material. These findings pose a concern for the nursery industry, indicating that the pathogen might be moving into regions with high red raspberry production.</div>